Circulating levels of the anti-oxidant indoleproprionic acid are associated with higher gut microbiome diversity

Identification of renal protective gut microbiome derived-metabolites in diabetic chronic kidney disease: An integrated approach using network pharmacology and molecular docking

Metabolites from the gut microbiota define molecules in the gut-kidney cross talks. However, the mechanistic pathway by which the kidneys actively sense gut metabolites and their impact on diabetic chronic kidney disease (DCKD) remains unclear. This study is an attempt to investigate the gut microbiome metabolites, their host targeting genes, and their mechanistic action against DCKD. Gut microbiome, metabolites, and host targets were extracted from the gutMgene database and metabolites from the PubChem database. DCKD targets were identified from DisGeNET, GeneCard, NCBI, and OMIM databases. Computational examination such as protein-protein interaction networks, enrichment pathway, identification of metabolites for potential targets using molecular docking, hubgene-microbes-metabolite-samplesource-substrate (HMMSS) network architecture were executed using Network analyst, ShinyGo, GeneMania, Cytoscape, Autodock tools. There were 574 microbial metabolites, 2861 DCKD targets, and 222 microbes targeting host genes. After screening, we obtained 27 final targets, which are used for computational examination. From enrichment analysis, we found NF-ΚB1, AKT1, EGFR, JUN, and RELA as the main regulators in the DCKD development through mitogen activated protein kinase (MAPK) pathway signalling. The (HMMSS) network analysis found F.prausnitzi, B.adolescentis, and B.distasonis probiotic bacteria that are found in the intestinal epithelium, colonic region, metabolize the substrates like tryptophan, other unknown substrates might have direct interaction with the NF-kB1 and epidermal growth factor receptor (EGFR) targets. On docking of these target proteins with 3- Indole propionic acid (IPA) showed high binding energy affinity of -5.9 kcal/mol and -7.4kcal/mol. From this study we identified, the 3 IPA produced by F. prausnitzi A2-165 was found to have renal sensing properties inhibiting MAPK/NF-KB1 inflammatory pathway and would be useful in treating CKD in diabetics.

Dietary fibre directs microbial tryptophan metabolism via metabolic interactions in the gut microbiota

Tryptophan is catabolized by gut microorganisms resulting in a wide range of metabolites implicated in both beneficial and adverse host effects. How gut microbial tryptophan metabolism is directed towards indole, associated with chronic kidney disease, or towards protective indolelactic acid (ILA) and indolepropionic acid (IPA) is unclear. Here we used in vitro culturing and animal experiments to assess gut microbial competition for tryptophan and the resulting metabolites in a controlled three-species defined community and in complex undefined human faecal communities. The generation of specific tryptophan-derived metabolites was not predominantly determined by the abundance of tryptophan-metabolizing bacteria, but rather by substrate-dependent regulation of specific metabolic pathways. Indole-producing Escherichia coli and ILA- and IPA-producing Clostridium sporogenes competed for tryptophan within the three-species community in vitro and in vivo. Importantly, fibre-degrading Bacteroides thetaiotaomicron affected this competition by cross-feeding monosaccharides to E. coli. This inhibited indole production through catabolite repression, thus making more tryptophan available to C. sporogenes, resulting in increased ILA and IPA production. The fibre-dependent reduction in indole was confirmed using human faecal cultures and faecal-microbiota-transplanted gnotobiotic mice. Our findings explain why consumption of fermentable fibres suppresses indole production but promotes the generation of other tryptophan metabolites associated with health benefits.

Decreased circulating IPA levels identify subjects with metabolic comorbidities: A multi-omics study

In recent years several experimental observations demonstrated that the gut microbiome plays a role in regulating positively or negatively metabolic homeostasis. Indole-3-propionic acid (IPA), a Tryptophan catabolic product mainly produced by C. Sporogenes, has been recently shown to exert either favorable or unfavorable effects in the context of metabolic and cardiovascular diseases. We performed a study to delineate clinical and multiomics characteristics of human subjects characterized by low and high IPA levels. Subjects with low IPA blood levels showed insulin resistance, overweight, low-grade inflammation, and features of metabolic syndrome compared to those with high IPA. Metabolomics analysis revealed that IPA was negatively correlated with leucine, isoleucine, and valine metabolism. Transcriptomics analysis in colon tissue revealed the enrichment of several signaling, regulatory, and metabolic processes. Metagenomics revealed several OTU of ruminococcus, alistipes, blautia, butyrivibrio and akkermansia were significantly enriched in highIPA group while in lowIPA group Escherichia-Shigella, megasphera, and Desulfovibrio genus were more abundant. Next, we tested the hypothesis that treatment with IPA in a mouse model may recapitulate the observations of human subjects, at least in part. We found that a short treatment with IPA (4 days at 20/mg/kg) improved glucose tolerance and Akt phosphorylation in the skeletal muscle level, while regulating blood BCAA levels and gene expression in colon tissue, all consistent with results observed in human subjects stratified for IPA levels. Our results suggest that treatment with IPA may be considered a potential strategy to improve insulin resistance in subjects with dysbiosis.

Machine Learning Metabolomics Profiling of Dietary Interventions from a Six-Week Randomised Trial

Metabolomics can uncover physiological responses to prebiotic fibre and omega-3 fatty acid supplements with known health benefits and identify response-specific metabolites. We profiled 534 stool and 799 serum metabolites in 64 healthy adults following a 6-week randomised trial comparing daily omega-3 versus inulin supplementation. Elastic net regressions were used to separately identify the serum and stool metabolites whose change in concentration discriminated between the two types of supplementations. Random forest was used to explore the gut microbiome's contribution to the levels of the identified metabolites from matching stool samples. Changes in serum 3-carboxy-4-methyl-5-propyl-2-furanpropanoate and indoleproprionate levels accurately discriminated between fibre and omega-3 (area under the curve (AUC) = 0.87 [95% confidence interval (CI): 0.63-0.99]), while stool eicosapentaenoate indicated omega-3 supplementation (AUC = 0.86 [95% CI: 0.64-0.98]). Univariate analysis also showed significant increases in indoleproprionate with fibre, 3-carboxy-4-methyl-5-propyl-2-furanpropanoate, and eicosapentaenoate with omega-3. Out of these, only the change in indoleproprionate was partly explained by changes in the gut microbiome composition (AUC = 0.61 [95% CI: 0.58-0.64] and Rho = 0.21 [95% CI: 0.08-0.34]) and positively correlated with the increase in the abundance of the genus Coprococcus (p = 0.005). Changes in three metabolites discriminated between fibre and omega-3 supplementation. The increase in indoleproprionate with fibre was partly explained by shifts in the gut microbiome, particularly Coprococcus, previously linked to better health.

The Effect of Type 2 Resistant Starch and Indole-3-Propionic Acid on Ameliorating High-Fat-Diet-Induced Hepatic Steatosis and Gut Dysbiosis

Owing to the interplay of genetic and environmental factors, obesity has emerged as a significant global public health concern. To gain enhanced control over obesity, we examined the effects of type 2 resistant starch (RS2) and its promoted microbial-derived metabolite, indole-3-propionic acid (IPA), on hepatic steatosis, antioxidant activity, and gut microbiota in obese mice. Neither RS2 nor low-dose IPA (20 mg kg-1) exhibited a reduction in body weight or improved glucose and lipid metabolism in post-obesity state mice continuously fed the high-fat diet (HFD). However, both interventions improved hepatic steatosis, with RS2 being more effective in all measured parameters, potentially due to changes in gut microbiota and metabolites not solely attributed to IPA. LC-MS/MS analysis revealed increased serum IPA levels in both RS2 and IPA groups, which positively correlated with Bifidobacterium and Clostridium. Moreover, RS2 exhibited a more significant restoration of gut dysbiosis by promoting the abundance of health-promoting bacteria including Faecalibaculum and Bifidobacterium. These findings suggest that the regulatory role of RS2 on tryptophan metabolism only partially explains its prebiotic activity. Future studies should consider increasing the dose of IPA and combining RS2 and IPA to explore their potential interventions in obesity.

Serum-Derived Bovine Immunoglobulin Promotes Barrier Integrity and Lowers Inflammation for 24 Human Adults Ex Vivo

Serum-derived bovine immunoglobulin (SBI) prevents translocation and inflammation via direct binding of microbial components. Recently, SBI also displayed potential benefits through gut microbiome modulation. To confirm and expand upon these preliminary findings, SBI digestion and colonic fermentation were investigated using the clinically predictive ex vivo SIFR® technology (for 24 human adults) that was, for the first time, combined with host cells (epithelial/immune (Caco-2/THP-1) cells). SBI (human equivalent dose (HED) = 2 and 5 g/day) and the reference prebiotic inulin (IN; HED = 2 g/day) significantly promoted gut barrier integrity and did so more profoundly than a dietary protein (DP), especially upon LPS-induced inflammation. SBI also specifically lowered inflammatory markers (TNF-α and CXCL10). SBI and IN both enhanced SCFA (acetate/propionate/butyrate) via specific gut microbes, while SBI specifically stimulated valerate/bCFA and indole-3-propionic acid (health-promoting tryptophan metabolite). Finally, owing to the high-powered cohort (n = 24), treatment effects could be stratified based on initial microbiota composition: IN exclusively stimulated (acetate/non-gas producing) Bifidobacteriaceae for subjects classifying as Bacteroides/Firmicutes-enterotype donors, coinciding with high acetate/low gas production and thus likely better tolerability of IN. Altogether, this study strongly suggests gut microbiome modulation as a mechanism by which SBI promotes health. Moreover, the SIFR® technology was shown to be a powerful tool to stratify treatment responses and support future personalized nutrition approaches.

Influence of Bariatric Surgery on Gut Microbiota Composition and Its Implication on Brain and Peripheral Targets

Obesity remains a significant global health challenge, with bariatric surgery remaining as one of the most effective treatments for severe obesity and its related comorbidities. This review highlights the multifaceted impact of bariatric surgery beyond mere physical restriction or nutrient malabsorption, underscoring the importance of the gut microbiome and neurohormonal signals in mediating the profound effects on weight loss and behavior modification. The various bariatric surgery procedures, such as Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG), act through distinct mechanisms to alter the gut microbiome, subsequently impacting metabolic health, energy balance, and food reward behaviors. Emerging evidence has shown that bariatric surgery induces profound changes in the composition of the gut microbiome, notably altering the Firmicutes/Bacteroidetes ratio and enhancing populations of beneficial bacteria such as Akkermansia. These microbiota shifts have far-reaching effects beyond gut health, influencing dopamine-mediated reward pathways in the brain and modulating the secretion and action of key gut hormones including ghrelin, leptin, GLP-1, PYY, and CCK. The resultant changes in dopamine signaling and hormone levels contribute to reduced hedonic eating, enhanced satiety, and improved metabolic outcomes. Further, post-bariatric surgical effects on satiation targets are in part mediated by metabolic byproducts of gut microbiota like short-chain fatty acids (SCFAs) and bile acids, which play a pivotal role in modulating metabolism and energy expenditure and reducing obesity-associated inflammation, as well as influencing food reward pathways, potentially contributing to the regulation of body weight and reduction in hedonic eating behaviors. Overall, a better understanding of these mechanisms opens the door to developing non-surgical interventions that replicate the beneficial effects of bariatric surgery on the gut microbiome, dopamine signaling, and gut hormone regulation, offering new avenues for obesity treatment.

Essential oil supplementation in milk replacers: short- and long-term impacts on feed efficiency, the faecal microbiota and the plasma metabolome in dairy calves

Early supplementation with oregano essential oil (EO) in milk replacer (MR) may improve growth, immune responses, the microbiota and the metabolome in dairy calves during pre-weaning and in adulthood. Sixteen female dairy calves (3 days of age) were divided in two groups (n = 8/group): the control group (no EO) and the EO group (0.23 ml of EO in MR during 45 days). After weaning, calves were kept in a feedlot and fed ad libitum. The animals were weighed, and blood and faecal samples were collected on days 3 (T0), 45 (T1) and 370 (T2) to measure the biochemical profile and characterise peripheral blood mononuclear cells (PBMCs; CD4+, CD8+, CD14+, CD21+ and WC1+), the metabolome and microbiota composition. The EO group only had greater average daily weight gain during the suckling (EO supplementation) period (P = 0.030). The EO group showed higher average CD14+ population (monocytes) values, a lower abundance of Ruminococcaceae UCG-014, Faecalibacterium, Blautia and Alloprevotella and increased abundances of Allistipes and Akkermansia. The modification of some metabolites in plasma, such as butyric acid, 3-indole-propionic acid and succinic acid, particularly at T1, are consistent with intestinal microbiota changes. The data suggest that early EO supplementation increases feed efficiency only during the suckling period with notable changes in the microbiota and plasma metabolome; however, not all of these changes can be considered desirable from a gut health point of view. Additional research studies is required to demonstrate that EOs are a viable natural alternative to antibiotics for improving calf growth performance and health.

Characteristics of Gut Microbiota in Patients with Erectile Dysfunction: A Chinese Pilot Study

PURPOSE

Little is known about the role of gut microbiota in the pathogenesis of erectile dysfunction (ED). We performed a study to compare taxonomic profiles of gut microbiota of ED and healthy males.

MATERIALS AND METHODS

A total of 43 ED patients and 16 healthy controls were enrolled in the study. The 5-item version of the International Index of Erectile Function (IIEF-5) with a cutoff value of 21 was used to evaluate erectile function. All participants underwent nocturnal penile tumescence and rigidity test. Samples of stool were sequenced to determine the gut microbiota.

RESULTS

We identified a distinct beta diversity of gut microbiome in ED patients by unweighted UniFrac analysis (R²=0.026, p=0.036). Linear discriminant analysis effect size (LEfse) analysis showed Actinomyces was significantly enriched, whereas Coprococcus_1, Lachnospiraceae_FCS020_group, Lactococcus, Ruminiclostridium_5, and Ruminococcaceae_UCG_002 were depleted in ED patients. Actinomyces showed a significant negative correlation with the duration of qualified erection, average maximum rigidity of tip, average maximum rigidity of base, tip tumescence activated unit (TAU), and base TAU. Coprococcus_1, Lachnospiraceae_FCS020_group, Ruminiclostridium_5, and Ruminococcaceae_UCG_002 were significantly correlated with the IIEF-5 score. Ruminiclostridium_5 and Ruminococcaceae_UCG_002 were positively related with average maximum rigidity of tip, average maximum rigidity of base, ΔTumescence of tip, and Tip TAU. Further, a random forest classifier based on the relative abundance of taxa showed good diagnostic efficacy with an area under curve of 0.72.

CONCLUSIONS

This pilot study identified evident alterations in the gut microbiome composition of ED patients and found Actinomyces was negatively correlated with erectile function, which may be a key pathogenic bacteria.

Microbiota-derived indoles alleviate intestinal inflammation and modulate microbiome by microbial cross-feeding

BACKGROUND

The host-microbiota interaction plays a crucial role in maintaining homeostasis and disease susceptibility, and microbial tryptophan metabolites are potent modulators of host physiology. However, whether and how these metabolites mediate host-microbiota interactions, particularly in terms of inter-microbial communication, remains unclear.

RESULTS

Here, we have demonstrated that indole-3-lactic acid (ILA) is a key molecule produced by Lactobacillus in protecting against intestinal inflammation and correcting microbial dysbiosis. Specifically, Lactobacillus metabolizes tryptophan into ILA, thereby augmenting the expression of key bacterial enzymes implicated in tryptophan metabolism, leading to the synthesis of other indole derivatives including indole-3-propionic acid (IPA) and indole-3-acetic acid (IAA). Notably, ILA, IPA, and IAA possess the ability to mitigate intestinal inflammation and modulate the gut microbiota in both DSS-induced and IL-10-/- spontaneous colitis models. ILA increases the abundance of tryptophan-metabolizing bacteria (e.g., Clostridium), as well as the mRNA expression of acyl-CoA dehydrogenase and indolelactate dehydrogenase in vivo and in vitro, resulting in an augmented production of IPA and IAA. Furthermore, a mutant strain of Lactobacillus fails to protect against inflammation and producing other derivatives. ILA-mediated microbial cross-feeding was microbiota-dependent and specifically enhanced indole derivatives production under conditions of dysbiosis induced by Citrobacter rodentium or DSS, but not of microbiota disruption with antibiotics.

CONCLUSION

Taken together, we highlight mechanisms by which microbiome-host crosstalk cooperatively control intestinal homoeostasis through microbiota-derived indoles mediating the inter-microbial communication. These findings may contribute to the development of microbiota-derived metabolites or targeted "postbiotic" as potential interventions for the treatment or prevention of dysbiosis-driven diseases. Video Abstract.

Effects of dietary energy level on antioxidant capability, immune function and rectal microbiota in late gestation donkeys

Introduction

This study investigated the effects of dietary energy level on the antioxidant capability, immune function, and rectal microbiota in donkey jennets during the last 60 days of gestation.

Methods

Fifteen pregnant DeZhou donkeys with age of 6.0 ± 0.1 years, body weight of 292 ± 33 kg, parity of 2.7 ± 0.1 parities and similar expected date of confinement (74 ± 4 days) were randomly allocated to three groups and feed three diets: high energy (10.92 MJ/kg, H), medium energy (10.49 MJ/kg, M), and low energy (9.94 MJ/kg, L).

Results and Discussion

The serum activity of catalase (CAT), total superoxide dismutase (T-SOD), glutathione peroxidase (GSH-Px), and total antioxidant capacity (T-AOC) in group M was significantly higher, whereas the concentrations of malondialdehyde (MDA), interleukin 1 (IL-1), IL-2, and IL-6 were lower than those recorded for groups H and L (p ≤ 0.05). The dietary energy level significantly affected rectal microbial community structure in the jennet donkeys 35 days and 7 days before the parturition (p ≤ 0.05). The abundances of norank_f_norank_o_Coriobacteriales genus was significantly higher (p ≤ 0.05) in group H, and the abundances of norank_f_norank_o_Mollicutes_RF39 and the Candidatus_Saccharimonas were higher in group L (p ≤ 0.05). The abundance of Fibrobacter in group M was significantly increased (p ≤ 0.05). The abundance of norank_f_norank_o_Coriobacteriales was positively correlated with average daily gain (ADG) and tumor necrosis factor-α (TNF-α) concentrations (p ≤ 0.05). The abundance of norank_f_norank_o_Mollicutes_RF39 was positively correlated with IL-2 and IL-6 concentrations. The abundance of Candidatus_Saccharimonas was positively correlated with CAT, T-SOD and GSH-Px activities (p ≤ 0.05). The abundance of Fibrobacter was positively correlated with CAT and T-SOD activities (p ≤ 0.05), but negatively correlated with IL-2 concentration (p ≤ 0.05). In conclusion, an appropriate dietary with an energy content of 10.49 MJ/kg for jennet donkeys during late gestation increased the prenatal antioxidant capacity, reduced inflammatory cytokines, and promoted fetal growth, and these changes were related to diet-induced changes in rectal microbiota compositions.

Tryptophan metabolism, gut microbiota, and carotid artery plaque in women with and without HIV infection

OBJECTIVE

The perturbation of tryptophan (TRP) metabolism has been linked with HIV infection and cardiovascular disease (CVD), but the interrelationship among TRP metabolites, gut microbiota, and atherosclerosis remain unclear in the context of HIV infection.

METHODS

We included 361 women (241 HIV+, 120 HIV-) with carotid artery plaque assessments from the Women's Interagency HIV Study, measured 10 plasma TRP metabolites and profiled fecal gut microbiome. TRP metabolite-related gut bacteria were selected through the Analysis of Compositions of Microbiomes with Bias Correction method. Associations of TRP metabolites and related microbial features with plaque were examined using multivariable logistic regression.

RESULTS

Although plasma kynurenic acid (KYNA) [odds ratio (OR) = 1.93, 95% confidence interval (CI): 1.12-3.32 per one SD increase; P  = 0.02) and KYNA/TRP [OR = 1.83 (95% CI 1.08-3.09), P  = 0.02] were positively associated with plaque, indole-3-propionate (IPA) [OR = 0.62 (95% CI 0.40-0.98), P  = 0.03] and IPA/KYNA [OR = 0.51 (95% CI 0.33-0.80), P  < 0.01] were inversely associated with plaque. Five gut bacterial genera and many affiliated species were positively associated with IPA (FDR-q < 0.25), including Roseburia spp ., Eubacterium spp., Lachnospira spp., and Coprobacter spp.; but no bacterial genera were found to be associated with KYNA. Furthermore, an IPA-associated-bacteria score was inversely associated with plaque [OR = 0.47 (95% CI 0.28-0.79), P  < 0.01]. But no significant effect modification by HIV serostatus was observed in these associations.

CONCLUSION

In a cohort of women living with and without HIV infection, plasma IPA levels and related gut bacteria were inversely associated with carotid artery plaque, suggesting a potential beneficial role of IPA and its gut bacterial producers in atherosclerosis and CVD.

The therapeutic potential of dietary intervention: based on the mechanism of a tryptophan derivative-indole propionic acid on metabolic disorders

Tryptophan (TRP) contributes to individual immune homeostasis and good condition via three complex metabolism pathways (5-hydroxytryptamine (5-HT), kynurenine (KP), and gut microbiota pathway). Indole propionic acid (IPA), one of the TRP derivatives of the microbiota pathway, has raised more attention because of its impact on metabolic disorders. Here, we retrospect increasing evidence that TRP metabolites/IPA derived from its proteolysis impact host health and disease. IPA can activate the immune system through aryl hydrocarbon receptor (AHR) and/or Pregnane X receptor (PXR) as a vital mediator among diet-caused host and microbe cross-talk. Different levels of IPA in systemic circulation can predict the risk of NAFLD, T2DM, and CVD. IPA is suggested to alleviate cognitive impairment from oxidative damage, reduce gut inflammation, inhibit lipid accumulation and attenuate the symptoms of NAFLD, putatively enhance the intestinal epithelial barrier, and maintain intestinal homeostasis. Now, we provide a general description of the relationships between IPA and various physiological and pathological processes, which support an opportunity for diet intervention for metabolic diseases.

Tryptophan metabolites and incident cardiovascular disease: The EPIC-Norfolk prospective population study

BACKGROUND AND AIMS

Cardiovascular disease (CVD) remains the largest cause of death globally due to various risk factors. One novel potential contributor to CVD might be the metabolism of the essential amino acid tryptophan (Trp), which through many pathways can produce immunomodulatory metabolites such as kynurenine, indole-3-propionate and serotonin. We aim to identify the metabolites with the strongest association with cardiovascular disease, utilizing a substantial and diverse cohort of individuals. In our pursuit of this aim, our primary focus is to validate and reinforce the findings from previous cross-sectional studies.

METHODS

We used the community-based EPIC-Norfolk cohort (46.3 % men, age 59.8 ± 9.0) with a median follow-up of 22.1 (17.6-23.3) years to study associations between the relative levels of Trp metabolites measured with untargeted metabolomics and incident development of CVD. Serum from n = 11,972 apparently healthy subjects was analysed, of which 6982 individuals had developed CVD at the end of follow-up. Cox proportional hazard models were used to study associations, adjusted for sex, age, conventional cardiovascular risk factors and CRP. All metabolites were Ln-normalised prior to analysis.

RESULTS

Higher levels of Trp were inversely associated with mortality (HR 0.73; CI 0.64-0.83) and fatal CVD (HR 0.76; CI 0.59-0.99). Higher levels of kynurenine (HR 1.33; CI 1.19-1.49) and the [Kynurenine]/[Tryptophan]-ratio (HR 1.24; CI 1.14-1.35) were associated with a higher incident development of CVD. Serotonin was not associated with overall CVD, but we did find associations for myocardial infarction and stroke. Adjustment for CRP did not yield any discernible differences in effect size.

CONCLUSIONS

Tryptophan levels were inversely correlated with CVD, while several of its major metabolites (especially kynurenine and serotonin) were positively correlated. These findings indicate that mechanistic studies are required to understand the role of Trp metabolism in CVD with the goal to identify new therapeutic targets.

Interplay between diet, circulating indolepropionate concentrations and cardiometabolic health in US populations

OBJECTIVES

To identify indolepropionate (IPA)-predicting gut microbiota species, investigate potential diet-microbiota interactions, and examine the prospective associations of circulating IPA concentrations with type 2 diabetes (T2D) and coronary heart disease (CHD) risk in free-living individuals.

DESIGN

We included 287 men from the Men's Lifestyle Validation Study, a substudy of the Health Professionals Follow-Up Study (HPFS), who provided up to two pairs of faecal samples and two blood samples. Diet was assessed using 7-day diet records. Associations between plasma concentrations of tryptophan metabolites and T2D CHD risk were examined in 13 032 participants from Nurses' Health Study (NHS), NHSII and HPFS.

RESULTS

We identified 17 microbial species whose abundance was significantly associated with plasma IPA concentrations. A significant association between higher tryptophan intake and higher IPA concentrations was only observed among men who had higher fibre intake and a higher microbial species score consisting of the 17 species (p-interaction<0.01). Dietary and plasma concentrations of tryptophan and most kynurenine pathway metabolites were positively associated with T2D risk (HRQ5 vs Q1 ranged from 1.17 to 1.46) while a significant inverse association was found for IPA (HRQ5 vs Q1 (95% CI) 0.70 (0.56 to 0.88)). No associations were found in CHD for any plasma tryptophan metabolites.

CONCLUSIONS

Specific microbial species and dietary fibre jointly predicted significantly higher circulating IPA concentrations at higher tryptophan intake. Dietary and plasma tryptophan, as well as its kynurenine pathway metabolites, demonstrated divergent associations from those for IPA, which was significantly predictive of lower risk of T2D.

Adipokines and Bacterial Metabolites: A Pivotal Molecular Bridge Linking Obesity and Gut Microbiota Dysbiosis to Target

Adipokines are essential mediators produced by adipose tissue and exert multiple biological functions. In particular, adiponectin, leptin, resistin, IL-6, MCP-1 and PAI-1 play specific roles in the crosstalk between adipose tissue and other organs involved in metabolic, immune and vascular health. During obesity, adipokine imbalance occurs and leads to a low-grade pro-inflammatory status, promoting insulin resistance-related diabetes and its vascular complications. A causal link between obesity and gut microbiota dysbiosis has been demonstrated. The deregulation of gut bacteria communities characterizing this dysbiosis influences the synthesis of bacterial substances including lipopolysaccharides and specific metabolites, generated via the degradation of dietary components, such as short-chain fatty acids, trimethylamine metabolized into trimethylamine-oxide in the liver and indole derivatives. Emerging evidence suggests that these bacterial metabolites modulate signaling pathways involved in adipokine production and action. This review summarizes the current knowledge about the molecular links between gut bacteria-derived metabolites and adipokine imbalance in obesity, and emphasizes their roles in key pathological mechanisms related to oxidative stress, inflammation, insulin resistance and vascular disorder. Given this interaction between adipokines and bacterial metabolites, the review highlights their relevance (i) as complementary clinical biomarkers to better explore the metabolic, inflammatory and vascular complications during obesity and gut microbiota dysbiosis, and (ii) as targets for new antioxidant, anti-inflammatory and prebiotic triple action strategies.

IBS randomized study: FODMAPs alter bile acids, phenolic- and tryptophan metabolites, while gluten modifies lipids

Diet is considered a culprit for symptoms in irritable bowel syndrome (IBS), although the mechanistic understanding of underlying causes is lacking. Metabolomics, i.e., the analysis of metabolites in biological samples may offer a diet-responsive fingerprint for IBS. Our aim was to explore alterations in the plasma metabolome after interventions with fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) or gluten versus control in IBS, and to relate such alterations to symptoms. People with IBS (n = 110) were included in a double-blind, randomized, crossover study with 1-wk provocations of FODMAPs, gluten, or placebo. Symptoms were evaluated with the IBS severity scoring system (IBS-SSS). Untargeted metabolomics was performed on plasma samples using LC-qTOF-MS. Discovery of metabolite alterations by treatment was performed using random forest followed by linear mixed modeling. Associations were studied using Spearman correlation. The metabolome was affected by FODMAP [classification rate (CR) 0.88, P < 0.0001], but less by gluten intake CR 0.72, P = 0.01). FODMAP lowered bile acids, whereas phenolic-derived metabolites and 3-indolepropionic acid (IPA) were higher compared with placebo. IPA and some unidentified metabolites correlated weakly to abdominal pain and quality of life. Gluten affected lipid metabolism weakly, but with no interpretable relationship to IBS. FODMAP affected gut microbial-derived metabolites relating to positive health outcomes. IPA and unknown metabolites correlated weakly to IBS severity. Minor symptom worsening by FODMAP intake must be weighed against general positive health aspects of FODMAP. The gluten intervention affected lipid metabolism weakly with no interpretable association to IBS severity. Registration: www.clinicaltrials.gov as NCT03653689.NEW & NOTEWORTHY In irritable bowel syndrome (IBS), fermentable oligo-, di-, monosaccharides, and polyols (FODMAPs) affected microbial-derived metabolites relating to positive health outcomes such as reduced risk of colon cancer, inflammation, and type 2 diabetes, as shown in previous studies. The minor IBS symptom induction by FODMAP intake must be weighed against the positive health aspects of FODMAP consumption. Gluten affected lipids weakly with no association to IBS severity.

Role of hypoxia in cellular senescence

Senescent cells persist and continuously secrete proinflammatory and tissue-remodeling molecules that poison surrounding cells, leading to various age-related diseases, including diabetes, atherosclerosis, and Alzheimer's disease. The underlying mechanism of cellular senescence has not yet been fully explored. Emerging evidence indicates that hypoxia is involved in the regulation of cellular senescence. Hypoxia-inducible factor (HIF)- 1α accumulates under hypoxic conditions and regulates cellular senescence by modulating the levels of the senescence markers p16, p53, lamin B1, and cyclin D1. Hypoxia is a critical condition for maintaining tumor immune evasion, which is promoted by driving the expression of genetic factors (such as p53 and CD47) while triggering immunosenescence. Under hypoxic conditions, autophagy is activated by targeting BCL-2/adenovirus E1B 19-kDa interacting protein 3, which subsequently induces p21WAF1/CIP1 as well as p16Ink4a and increases β-galactosidase (β-gal) activity, thereby inducing cellular senescence. Deletion of the p21 gene increases the activity of the hypoxia response regulator poly (ADP-ribose) polymerase-1 (PARP-1) and the level of nonhomologous end joining (NHEJ) proteins, repairs DNA double-strand breaks, and alleviates cellular senescence. Moreover, cellular senescence is associated with intestinal dysbiosis and an accumulation of D-galactose derived from the gut microbiota. Chronic hypoxia leads to a striking reduction in the amount of Lactobacillus and D-galactose-degrading enzymes in the gut, producing excess reactive oxygen species (ROS) and inducing senescence in bone marrow mesenchymal stem cells. Exosomal microRNAs (miRNAs) and long noncoding RNAs (lncRNAs) play important roles in cellular senescence. miR-424-5p levels are decreased under hypoxia, whereas lncRNA-MALAT1 levels are increased, both of which induce cellular senescence. The present review focuses on recent advances in understanding the role of hypoxia in cellular senescence. The effects of HIFs, immune evasion, PARP-1, gut microbiota, and exosomal mRNA in hypoxia-mediated cell senescence are specifically discussed. This review increases our understanding of the mechanism of hypoxia-mediated cellular senescence and provides new clues for anti-aging processes and the treatment of aging-related diseases.

Contribution of Circulating Host and Microbial Tryptophan Metabolites Toward Ah Receptor Activation

The aryl hydrocarbon receptor (AHR) is a ligand activated transcription factor that plays an integral role in homeostatic maintenance by regulating cellular functions such as cellular differentiation, metabolism, barrier function, and immune response. An important but poorly understood class of AHR activators are compounds derived from host and bacterial metabolism of tryptophan. The commensal bacteria of the gut microbiome are major producers of tryptophan metabolites known to activate the AHR, while the host also produces AHR activators through tryptophan metabolism. We used targeted mass spectrometry-based metabolite profiling to determine the presence and metabolic source of these metabolites in the sera of conventional mice, germ-free mice, and humans. Surprisingly, sera concentrations of many tryptophan metabolites are comparable between germ-free and conventional mice. Therefore, many major AHR-activating tryptophan metabolites in mouse sera are produced by the host, despite their presence in feces and mouse cecal contents. Here we present an investigation of AHR activation using a complex mixture of tryptophan metabolites to examine the biological relevance of circulating tryptophan metabolites. AHR activation is rarely studied in the context of a mixture at relevant concentrations, as we present here. The AHR activation potentials of individual and pooled metabolites were explored using cell-based assays, while ligand binding competition assays and ligand docking simulations were used to assess the detected metabolites as AHR agonists. The physiological and biomedical relevance of the identified metabolites was investigated in the context of a cell-based model for rheumatoid arthritis. We present data that reframe AHR biology to include the presence of a mixture of ubiquitous tryptophan metabolites, improving our understanding of homeostatic AHR activity and models of AHR-linked diseases.

Gut Microbiota and Microbial Metabolism in Early Risk of Cardiometabolic Disease

Cardiometabolic disease comprises cardiovascular and metabolic dysfunction and underlies the leading causes of morbidity and mortality, both within the United States and worldwide. Commensal microbiota are implicated in the development of cardiometabolic disease. Evidence suggests that the microbiome is relatively variable during infancy and early childhood, becoming more fixed in later childhood and adulthood. Effects of microbiota, both during early development, and in later life, may induce changes in host metabolism that modulate risk mechanisms and predispose toward the development of cardiometabolic disease. In this review, we summarize the factors that influence gut microbiome composition and function during early life and explore how changes in microbiota and microbial metabolism influence host metabolism and cardiometabolic risk throughout life. We highlight limitations in current methodology and approaches and outline state-of-the-art advances, which are improving research and building toward refined diagnosis and treatment options in microbiome-targeted therapies.

Gut microbiota indole-3-propionic acid mediates neuroprotective effect of probiotic consumption in healthy elderly: A randomized, double-blind, placebo-controlled, multicenter trial and in vitro study

BACKGROUND & AIMS

The beneficial effects of probiotic consumption on age-related decline in cerebral function have been previously reported in the literature; however, the mechanistic link between gut and brain interactions has not yet been fully elucidated. Therefore, this study aimed to identify the role of gut microbiota-derived metabolites in gut-brain interactions via blood metabolomic profiling analysis in clinical trials and in vitro mechanistic studies.

METHODS

A randomized, double-blind, placebo-controlled, multicenter clinical trial was conducted in 63 healthy elderly individuals (≥65 years of age). Participants were administered either placebo (placebo group, N = 31) or probiotic capsules (Bifidobacterium bifidum BGN4 and Bifidobacterium longum BORI; probiotics group, N = 32) for 12 weeks. Global and targeted metabolomic profiling analyses of their blood samples were then performed using ¹H nuclear magnetic resonance and liquid chromatography-mass spectrometry methods, both at baseline and at the end of the trial. Gut microbial analysis was conducted using the 16S ribosomal ribonucleic acid gene sequencing method. Subsequently, microglial BV2 cells were treated in vitro with indole-3-propionic acid (IPA) following lipopolysaccharide stimulation, and neuronal SH-SY5Y cells were treated with conditioned media from the BV2 cells. Finally, the levels of pro-inflammatory cytokines in BV2 cells and neurotrophins in SH-SY5Y cells were quantified using a real-time polymerase chain reaction or enzyme-linked immunosorbent assay.

RESULTS

The metabolomic profiling analyses showed that probiotic consumption significantly altered the levels of metabolites involved in tryptophan metabolism (P < 0.01). Among these metabolites, gut microbiota-produced IPA had a 1.91-fold increase in the probiotics group (P < 0.05) and showed a significant relation to gut bacterial profiles (P < 0.01). Elevated IPA levels were also positively associated with the level of serum brain-derived neurotropic factor (BDNF) in the probiotics group (r = 0.28, P < 0.05), showing an inverse trend compared to the placebo group. In addition, in vitro treatment with IPA (5 μM) significantly reduced the concentration of proinflammatory TNF-α in activated microglia (P < 0.05), and neuronal cells cultured with conditioned media from IPA-treated microglia showed a significant increase in BDNF and nerve growth factor production (P < 0.05).

CONCLUSIONS

These results show that gut microbiota-produced IPA plays a role in protecting the microglia from inflammation, thus promoting neuronal function. Therefore, this suggests that IPA is a significant mediator linking the interaction between the gut and the brain in the elderly with probiotic supplementation.

Astragalus polysaccharides alleviate type 1 diabetes via modulating gut microbiota in mice

Type 1 diabetes (T1D) is a serious health problem that needs to be addressed worldwide. Astragalus polysaccharides (APS), the main chemical components of Astragali Radix, have anti-diabetic activity. As most plant polysaccharides are difficult to digest and absorb, we hypothesised that APS exert hypoglycaemic effects through the gut. This study intends to investigate the modulation of T1D associated with gut microbiota by neutral fraction of Astragalus polysaccharides (APS-1). T1D mice were induced with streptozotocin and then treated with APS-1 for 8 weeks. Fasting blood glucose levels were decreased and the insulin levels were increased in T1D mice. The results demonstrated that APS-1 improved gut barrier function by regulating ZO-1, Occludin and Claudin-1 expression, and reconstructed gut microbiota by increasing the relative abundance of Muribaculum, Lactobacillus and Faecalibaculum. In addition, APS-1 significantly increased the levels of acetic acid, propionic acid, butyric acid and inhibited the expression of pro-inflammatory factors IL-6 and TNF-α in T1D mice. Further exploration revealed that APS-1 alleviation of T1D may be associated with short-chain fatty acids (SCFAs)-producing bacteria, and that SCFAs binds to GPRs and HDACs proteins and modulate the inflammatory responses. In conclusion, the study supports the potential of APS-1 as a therapeutic agent for T1D.

Benefits of Biotics for Cardiovascular Diseases

Cardiovascular diseases are the main cause of death in many countries, and the better prevention and prediction of these diseases would be of great importance for individuals and society. Nutrition, the gut microbiota, and metabolism have raised much interest in the field of cardiovascular disease research in the search for the main mechanisms that promote cardiovascular diseases. Understanding the interactions between dietary nutrient intake and the gut microbiota-mediated metabolism may provide clinical insight in order to identify individuals at risk of cardiometabolic disease progression, as well as other potential therapeutic targets to mitigate the risk of cardiometabolic disease progression. The development of cardiometabolic diseases can be modulated by specific beneficial metabolites derived from bacteria. Therefore, it is very important to investigate the impact of these metabolites on human health and the possibilities of modulating their production with dietary supplements called biotics.

2 Hydroxybutyric Acid-Producing Bacteria in Gut Microbiome and Fusobacterium nucleatum Regulates 2 Hydroxybutyric Acid Level In Vivo

2-hydroxybutyric acid (2HB) serves as an important regulatory factor in a variety of diseases. The circulating level of 2HB in serum is significantly higher in multiple diseases, such as cancer and type 2 diabetes (T2D). However, there is currently no systematic study on 2HB-producing bacteria that demonstrates whether gut bacteria contribute to the circulating 2HB pool. To address this question, we used BLASTP to reveal the taxonomic profiling of 2HB-producing bacteria in the human microbiome, which are mainly distributed in the phylum Proteobacteria and Firmicutes. In vitro experiments showed that most gut bacteria (21/32) have at least one path to produce 2HB, which includes Aspartic acid, methionine, threonine, and 2-aminobutyric acid. Particularly, Fusobacterium nucleatum has the strongest ability to synthesize 2HB, which is sufficient to alter colon 2HB concentration in mice. Nevertheless, neither antibiotic (ABX) nor Fusobacterium nucleatum gavage significantly affected mouse serum 2HB levels during the time course of this study. Taken together, our study presents the profiles of 2HB-producing bacteria and demonstrates that gut microbiota was a major contributor to 2HB concentration in the intestinal lumen but a relatively minor contributor to serum 2HB concentration.

Cannabinoids modulate the microbiota-gut-brain axis in HIV/SIV infection by reducing neuroinflammation and dysbiosis while concurrently elevating endocannabinoid and indole-3-propionate levels

BACKGROUND

Although the advent of combination anti-retroviral therapy (cART) has transformed HIV into a manageable chronic disease, an estimated 30-50% of people living with HIV (PLWH) exhibit cognitive and motor deficits collectively known as HIV-associated neurocognitive disorders (HAND). A key driver of HAND neuropathology is chronic neuroinflammation, where proinflammatory mediators produced by activated microglia and macrophages are thought to inflict neuronal injury and loss. Moreover, the dysregulation of the microbiota-gut-brain axis (MGBA) in PLWH, consequent to gastrointestinal dysfunction and dysbiosis, can lead to neuroinflammation and persistent cognitive impairment, which underscores the need for new interventions.

METHODS

We performed RNA-seq and microRNA profiling in basal ganglia (BG), metabolomics (plasma) and shotgun metagenomic sequencing (colon contents) in uninfected and SIV-infected rhesus macaques (RMs) administered vehicle (VEH/SIV) or delta-9-tetrahydrocannabinol (THC) (THC/SIV).

RESULTS

Long-term, low-dose THC reduced neuroinflammation and dysbiosis and significantly increased plasma endocannabinoid, endocannabinoid-like, glycerophospholipid and indole-3-propionate levels in chronically SIV-infected RMs. Chronic THC potently blocked the upregulation of genes associated with type-I interferon responses (NLRC5, CCL2, CXCL10, IRF1, IRF7, STAT2, BST2), excitotoxicity (SLC7A11), and enhanced protein expression of WFS1 (endoplasmic reticulum stress) and CRYM (oxidative stress) in BG. Additionally, THC successfully countered miR-142-3p-mediated suppression of WFS1 protein expression via a cannabinoid receptor-1-mediated mechanism in HCN2 neuronal cells. Most importantly, THC significantly increased the relative abundance of Firmicutes and Clostridia including indole-3-propionate (C. botulinum, C. paraputrificum, and C. cadaveris) and butyrate (C. butyricum, Faecalibacterium prausnitzii and Butyricicoccus pullicaecorum) producers in colonic contents.

CONCLUSION

This study demonstrates the potential of long-term, low-dose THC to positively modulate the MGBA by reducing neuroinflammation, enhancing endocannabinoid levels and promoting the growth of gut bacterial species that produce neuroprotective metabolites, like indole-3-propionate. The findings from this study may benefit not only PLWH on cART, but also those with no access to cART and more importantly, those who fail to suppress the virus under cART.

Serum-Derived Bovine Immunoglobulin Stimulates SCFA Production by Specific Microbes in the Ex Vivo SIFR® Technology

Serum-derived bovine immunoglobulins (SBI) exert health benefits mediated by their ability to bind microbial components, thereby preventing translocation and subsequent inflammation. While in vivo studies have shown that a fraction of SBI also reaches the colon, little is known about the impact of SBI on the dense colonic microbiota that has great potential to impact human health. This study, therefore, investigated the impact of three bovine plasma protein fractions (SBI, bovine plasma (BP) and albumin-enriched bovine plasma (ABP)) on the gut microbiota of six human adults using the novel ex vivo SIFR® technology, recently demonstrated to generate predictive findings for clinical studies. When dosed at an equivalent of 5 g/day, all protein fractions significantly increased health-related metabolites—acetate, propionate, and butyrate. Upon simulating small intestinal absorption, SBI still markedly increased acetate and propionate, demonstrating that SBI is more resistant to small intestinal digestion and absorption compared to the other protein sources. Despite noticeable interindividual differences in microbiota composition among human adults, SBI consistently stimulated a narrow spectrum of gut microbes, which largely differed from the ones that are typically involved in carbohydrate fermentation. The SBI-fermenting consortium included B. vulgatus and L. edouardi (correlating with acetate and propionate) along with Dorea longicatena, Coprococcus comes and the butyrate-producing bacterium SS3/4 (correlating with butyrate). Overall, this study revealed that protein bovine fractions can contribute to health benefits by specifically modulating the human gut microbiota. While health benefits could follow from the production of SCFA, a broader range of protein-derived metabolites could also be produced. This study also confirms that the concept of prebiotics (substrates selectively utilized by host microorganisms conferring a health benefit) could go beyond the use of ingestible carbohydrates and extend to partially indigestible proteins.

Gut Microbiota and Their Associated Metabolites in Diabetes: A Cross Talk Between Host and Microbes-A Review

Dysbiosis of the gut microbiota's composition and function is important in developing insulin resistance and diabetes. Diabetes has also been linked to changes in the circulating and fecal metabolites. Evidence suggests the associations between the gut microbiota and the aberrant diabetes-related metabolome. Metabolites play a crucial role in the host-microbiota interactions. Researchers have used a combination of metagenomic and metabolomic approaches to investigate the relationships between gut microbial dysbiosis and metabolic abnormalities in diabetes. We summarized current discoveries on the associations between the gut microbiota and metabolites in type 1 diabetes, type 2 diabetes, and gestational diabetes mellitus in the scoping review. According to research, the gut microbiota changes might involve in the development of diabetes through modulating the host's metabolic pathways such as immunity, energy metabolism, lipid metabolism, and amino acid metabolism. These results add to our understanding of the interplay between the host and gut microbiota metabolism.

Contribution of circulating host and microbial tryptophan metabolites towards Ah receptor activation

The aryl hydrocarbon receptor (AHR) is a ligand activated transcription factor that plays an integral role in homeostatic maintenance by regulating cellular functions such as cellular differentiation, metabolism, barrier function, and immune response. An important but poorly understood class of AHR activators are compounds derived from host and bacterial metabolism of tryptophan. The commensal bacteria of the gut microbiome are major producers of tryptophan metabolites known to activate the AHR, while the host also produces AHR activators through tryptophan metabolism. We used targeted mass spectrometry-based metabolite profiling to determine the presence and metabolic source of these metabolites in the sera of conventional mice, germ-free mice, and humans. Surprisingly, sera concentrations of many tryptophan metabolites are comparable between germ-free and conventional mice. Therefore, many major AHR-activating tryptophan metabolites in mouse sera are produced by the host, despite their presence in feces and mouse cecal contents. AHR activation is rarely studied in the context of a mixture at relevant concentrations, as we present here. The AHR activation potentials of individual and pooled metabolites were explored using cell-based assays, while ligand binding competition assays and ligand docking simulations were used to assess the detected metabolites as AHR agonists. The physiological and biomedical relevance of the identified metabolites was investigated in the context of cell-based models for cancer and rheumatoid arthritis. We present data here that reframe AHR biology to include the presence of ubiquitous tryptophan metabolites, improving our understanding of homeostatic AHR activity and models of AHR-linked diseases.

Two-week repair alleviates hexavalent chromium-induced hepatotoxicity, hepatic metabolic and gut microbial changes: A dynamic inhalation exposure model in male mice

Hexavalent chromium [Cr(VI)] has been identified as a "Group I human carcinogen" with multisystem and multiorgan toxicity. A dynamic inhalation exposure model in male mice, coupled with the hepatic metabolome and gut microbiome, was used to explore hepatotoxicity, and hepatic metabolic and gut microbial changes under the exposure scenarios in the workspace and general environment. The present study set up an exposure group (EXP) that inhaled 150 μg Cr/m³ for 13 weeks, a control group (CONT) that inhaled purified air, as well as a two-week repair group (REXP) after 13 weeks of exposure and the corresponding control group (RCONT). Cr(VI) induced elevation of hepatic Cr accumulation, the ratio of ALT and AST, and folate in serum. Inflammatory infiltration in the liver and abnormal mitochondria in hepatocytes were also induced by Cr(VI). Glutathione, ascorbate, folic acid, pantetheine, 3'-dephospho-CoA and citraconic acid were the key metabolites affected by Cr(VI) that were associated with significant pathways such as pantothenate and CoA biosynthesis, hypoxia-inducible factor-1 signaling pathway, antifolate resistance, alpha-linolenic acid metabolism and one carbon pool by folate. g_Allobaculum was identified as a sensitive biomarker of Cr(VI) exposure because g_Allobaculum decreased under Cr(VI) exposure but increased after repair. The gut microbiota might be involved in the compensation of hepatotoxicity by increasing short-chain fatty acid-producing bacteria, including g_Lachnospiraceae_NK4A136_group, g_Blautia, and f_Muribaculaceae. After the two-week repair, the differential metabolites between the exposed and control groups were reduced from 73 to 29, and the KEGG enrichment pathways and differential microbiota also decreased. The mechanism for repair was associated with reversion of lipid peroxidation and energy metabolism, as well as activation of protective metabolic pathways, such as the AMPK signaling pathway, longevity regulating pathway, and oxidative phosphorylation. These findings might have theoretical and practical implications for better health risk assessment and management.

Extensive Summary of the Important Roles of Indole Propionic Acid, a Gut Microbial Metabolite in Host Health and Disease

Increasing evidence suggests that metabolites produced by the gut microbiota play a crucial role in host-microbe interactions. Dietary tryptophan ingested by the host enters the gut, where indole-like metabolites such as indole propionic acid (IPA) are produced under deamination by commensal bacteria. Here, we summarize the IPA-producing bacteria, dietary patterns on IPA content, and functional roles of IPA in various diseases. IPA can not only stimulate the expression of tight junction (TJ) proteins to enhance gut barrier function and inhibit the penetration of toxic factors, but also modulate the immune system to exert anti-inflammatory and antioxidant effects to synergistically regulate body physiology. Moreover, IPA can act on target organs through blood circulation to form the gut-organ axis, which helps maintain systemic homeostasis. IPA shows great potential for the diagnosis and treatment of various clinical diseases, such as NAFLD, Alzheimer's disease, and breast cancer. However, the therapeutic effect of IPA depends on dose, target organ, or time. In future studies, further work should be performed to explore the effects and mechanisms of IPA on host health and disease to further improve the existing treatment program.

Associations of microbial and indoleamine-2,3-dioxygenase-derived tryptophan metabolites with immune activation in healthy adults

Background

Tryptophan (Trp) metabolites from intestinal bacteria (indole, indole acetic acid [IAA] and indole propionic acid [IPA]), and the Trp metabolite kynurenine (Kyn) from the indoleamine 2,3-dioxygenase (IDO) pathway, are aryl hydrocarbon receptor (AhR) agonists and thus, can regulate immune activity via the AhR pathway. We hypothesized that plasma concentrations of these metabolites would be associated with markers of immune activation in a cohort of healthy adults in a manner consistent with AhR-mediated immune-regulation. We also hypothesized that the plasma Kyn/Trp ratio, a marker of IDO activity, would be associated with immune markers reflecting IDO activation in innate immune cells. Finally, we hypothesized that some intestinal bacteria would be associated with plasma indole, IPA and IAA, and that these bacteria themselves would be associated with immune markers.

Methods

A novel set of 88 immune markers, and plasma Trp metabolites, were measured in 362 healthy adults. Bacterial taxa from stool were identified by 16S rRNA gene analysis. Multiple linear regression analysis was used to identify significant associations with immune markers.

Results

The sum of indole and IAA was positively associated with natural killer T-cells levels. Kyn and Kyn/Trp were positively associated with neopterin and IP-10, markers of type 1 immunity, and TNF-α and C-reactive protein (CRP), markers of the acute phase response, and the regulatory cytokine IL-10. Three bacteria negatively associated with Trp metabolites were associated with markers of immune activation: the family Lachnospiraceae with higher lymphocyte counts but lower level of activated CD4 T-cells, the genus Dorea with higher production of IFN-γ by T-cells in PBMC cultures, and the genus Ruminococcus with higher production IL-6 in PBMC cultures stimulated with bacterial lipopolysaccharide (LPS).

Conclusions

In this cohort of healthy adults bacterial Trp metabolites were not strongly associated with immune markers. Conversely, the Kyn/Trp ratio was strongly associated with markers of systemic inflammation and the acute phase response, consistent with IDO activation in innate immune cells. Finally, commensal bacteria associated with lower plasma (and perhaps intestinal) levels of bacterial Trp metabolites were associated with greater immune activation, possibly reflecting decreased regulatory immune activity related to lower intestinal levels of bacterial indole metabolites.

Gut and obesity/metabolic disease: Focus on microbiota metabolites

Obesity is often associated with the risk of chronic inflammation and other metabolic diseases, such as diabetes, cardiovascular disease, and cancer. The composition and activity of the gut microbiota play an important role in this process, affecting a range of physiological processes, such as nutrient absorption and energy metabolism. The active gut microbiota can produce a large number of physiologically active substances during the process of intestinal metabolism and reproduction, including short‐chain/long‐chain fatty acids, secondary bile acids, and tryptophan metabolites with beneficial effects on metabolism, as well as negative metabolites, including trimethylamine N‐oxide, delta‐valerobetaine, and imidazole propionate. How gut microbiota specifically affect and participate in metabolic and immune activities, especially the metabolites directly produced by gut microbiota, has attracted extensive attention. So far, some animal and human studies have shown that gut microbiota metabolites are correlated with host obesity, energy metabolism, and inflammation. Some pathways and mechanisms are slowly being discovered. Here, we will focus on the important metabolites of gut microbiota (beneficial and negative), and review their roles and mechanisms in obesity and related metabolic diseases, hoping to provide a new perspective for the treatment and remission of obesity and other metabolic diseases from the perspective of metabolites.

Gut Microbially Produced Indole-3-Propionic Acid Inhibits Atherosclerosis by Promoting Reverse Cholesterol Transport and Its Deficiency Is Causally Related to Atherosclerotic Cardiovascular Disease

BACKGROUND

Accumulating evidence has shown that disorders in the gut microbiota and derived metabolites affect the development of atherosclerotic cardiovascular disease (ASCVD). However, which and how specific gut microbial metabolites contribute to the progression of atherosclerosis and the clinical relevance of their alterations remain unclear.

METHODS

We performed integrated microbiome-metabolome analysis of 30 patients with coronary artery disease (CAD) and 30 age- and sex-matched healthy controls to identify CAD-associated microbial metabolites, which were then assessed in an independent population of patients with ASCVD and controls (n=256). We further investigate the effect of CAD-associated microbial metabolites on atherosclerosis and the mechanisms of the action.

RESULTS

Indole-3-propionic acid (IPA), a solely microbially derived tryptophan metabolite, was the most downregulated metabolite in patients with CAD. Circulating IPA was then shown in an independent population to be associated with risk of prevalent ASCVD and correlated with the ASCVD severity. Dietary IPA supplementation alleviates atherosclerotic plaque development in ApoE^-/- mice. In murine- and human-derived macrophages, administration of IPA promoted cholesterol efflux from macrophages to ApoA-I through an undescribed miR-142-5p/ABCA1 (ATP-binding cassette transporter A1) signaling pathway. Further in vivo studies demonstrated that IPA facilitates macrophage reverse cholesterol transport, correlating with the regulation of miR-142-5p/ABCA1 pathway, whereas reduced IPA production contributed to the aberrant overexpression of miR-142-5p in macrophages and accelerated the progression of atherosclerosis. Moreover, the miR-142-5p/ABCA1/reverse cholesterol transport axis in macrophages were dysregulated in patients with CAD, and correlated with the changes in circulating IPA levels.

CONCLUSIONS

Our study identify a previously unknown link between specific gut microbiota-derived tryptophan metabolite and ASCVD. The microbial metabolite IPA/miR-142-5p/ABCA1 pathway may represent a promising therapeutic target for ASCVD.

Shenling Baizhu San ameliorates ulcerative colitis by regulating the gut microbiota and its tryptophan metabolites: A complementary medicine to mesalamine

ETHNOPHARMACOLOGICAL RELEVANCE

Shenling Baizhu San (SBS) is commonly employed to improve gastrointestinal dysfunction in patients with ulcerative colitis (UC) in China. SBS combined with mesalamine has been demonstrated to result in improve its curative effects without increasing any adverse reactions, but the underlying mechanism remains unclarified.

AIM OF THE STUDY

Our study aimed to illuminate the potential therapeutic effects and mechanisms of SBS, which is a medicine complementary to mesalamine, in the treatment of UC.

MATERIALS AND METHODS

A prospective cohort study was conducted to evaluate the efficacy of SBS as a complementary medicine to mesalamine for patients with UC (n = 48). The patients in the control group (n = 24) were given mesalamine alone, whereas those in the experimental group were administered mesalamine combined with SBS. The therapeutic outcome was assessed at 8 weeks. The structures of the gut microbiota (GMB) were characterized by 16S rRNA sequencing, and the microbial tryptophan metabolites were analyzed by UPLC-MS/MS to investigate the mechanism through which SBS achieves its effects.

RESULTS

Our results showed that the combination of SBS and mesalamine could significantly improve the clinical signs of UC by achieving mucosal healing and relieving colon damage. Interestingly, the combination of SBS and mesalamine could alter the GMB structures and increase the microbial levels of tryptophan metabolites, including indole-3-propionic acid and indole-3-acetic acid.

CONCLUSION

SBS combined with mesalamine is effective in improving the clinical and endoscopic outcomes of patients with UC. SBS, as a complementary therapy to conventional treatment, alleviates UC via the GMB-tryptophan metabolite axis.

External light‐dark cycle shapes gut microbiota through intrinsically photosensitive retinal ganglion cells

Gut microbiota are involved in many physiological functions such as metabolism, brain development, and neurodegenerative diseases. Many microbes in the digestive tract do not maintain a constant level of their relative abundance but show daily oscillations under normal conditions. Recent evidence indicates that chronic jetlag, constant darkness, or deletion of the circadian core gene can alter the composition of gut microbiota and dampen the daily oscillation of gut microbes. However, the neuronal circuit responsible for modulating gut microbiota remained unclear. Using genetic mouse models and 16s rRNA metagenomic analysis, we find that light-dark cycle information transmitted by the intrinsically photosensitive retinal ganglion cells (ipRGCs) is essential for daily oscillations of gut microbes under temporal restricted high-fat diet conditions. Furthermore, aberrant light exposure such as dim light at night (dLAN) can alter the composition, relative abundance, and daily oscillations of gut microbiota. Together, our results indicate that external light-dark cycle information can modulate gut microbiota in the direction from the brain to the gut via the sensory system.

Host and gut microbial tryptophan metabolism and type 2 diabetes: an integrative analysis of host genetics, diet, gut microbiome and circulating metabolites in cohort studies

OBJECTIVE

Tryptophan can be catabolised to various metabolites through host kynurenine and microbial indole pathways. We aimed to examine relationships of host and microbial tryptophan metabolites with incident type 2 diabetes (T2D), host genetics, diet and gut microbiota.

METHOD

We analysed associations between circulating levels of 11 tryptophan metabolites and incident T2D in 9180 participants of diverse racial/ethnic backgrounds from five cohorts. We examined host genome-wide variants, dietary intake and gut microbiome associated with these metabolites.

RESULTS

Tryptophan, four kynurenine-pathway metabolites (kynurenine, kynurenate, xanthurenate and quinolinate) and indolelactate were positively associated with T2D risk, while indolepropionate was inversely associated with T2D risk. We identified multiple host genetic variants, dietary factors, gut bacteria and their potential interplay associated with these T2D-relaetd metabolites. Intakes of fibre-rich foods, but not protein/tryptophan-rich foods, were the dietary factors most strongly associated with tryptophan metabolites. The fibre-indolepropionate association was partially explained by indolepropionate-associated gut bacteria, mostly fibre-using Firmicutes. We identified a novel association between a host functional LCT variant (determining lactase persistence) and serum indolepropionate, which might be related to a host gene-diet interaction on gut Bifidobacterium, a probiotic bacterium significantly associated with indolepropionate independent of other fibre-related bacteria. Higher milk intake was associated with higher levels of gut Bifidobacterium and serum indolepropionate only among genetically lactase non-persistent individuals.

CONCLUSION

Higher milk intake among lactase non-persistent individuals, and higher fibre intake were associated with a favourable profile of circulating tryptophan metabolites for T2D, potentially through the host-microbial cross-talk shifting tryptophan metabolism toward gut microbial indolepropionate production.

Influence of Natural Polysaccharides on Intestinal Microbiota in Inflammatory Bowel Diseases: An Overview

The incidence of inflammatory bowel disease (IBD) has increased in recent years. Considering the potential side effects of conventional drugs, safe and efficient treatment methods for IBD are required urgently. Natural polysaccharides (NPs) have attracted considerable attention as potential therapeutic agents for IBD owing to their high efficiency, low toxicity, and wide range of biological activities. Intestinal microbiota and their fermentative products, mainly short-chain fatty acids (SCFAs), are thought to mediate the effect of NPs in IBDs. This review explores the beneficial effects of NPs on IBD, with a special focus on the role of intestinal microbes. Intestinal microbiota exert alleviation effects via various mechanisms, such as increasing the intestinal immunity, anti-inflammatory activities, and intestinal barrier protection via microbiota-dependent and microbiota-independent strategies. The aim of this paper was to document evidence of NP–intestinal microbiota-associated IBD prevention, which would be helpful for guidance in the treatment and management of IBD.

Analysis of the gut microbiota composition of myostatin mutant cattle prepared using CRISPR/Cas9

Myostatin (MSTN) negatively regulates muscle development and positively regulates metabolism through various pathways. Although MSTN function in cattle has been widely studied, the changes in the gut microbiota due to MSTN mutation, which contribute to host health by regulating its metabolism, remain unclear. Here, high-throughput sequencing of the 16S rRNA gene was conducted to analyze the gut microbiota of wild-type (WT) and MSTN mutant (MT) cattle. A total of 925 operational taxonomic units (OTUs) were obtained, which were classified into 11 phyla and 168 genera. Alpha diversity results showed no significant differences between MT and WT cattle. Beta diversity analyses suggested that the microbial composition of WT and MT cattle was different. Three dominant phyla and 21 dominant genera were identified. The most abundant bacterial genus had a significant relationship with the host metabolism. Moreover, various bacteria beneficial for health were found in the intestines of MT cattle. Analysis of the correlation between dominant gut bacteria and serum metabolic factors affected by MSTN mutation indicated that MSTN mutation affected the metabolism mainly by three metabolism-related bacteria, Ruminococcaceae_UCG-013, Clostridium_sensu_stricto_1, and Ruminococcaceae_UCG-010. This study provides further insight into MSTN mutation regulating the host metabolism by gut microbes and provides evidence for the safety of gene-edited animals.

Taxifolin Alleviates DSS-Induced Ulcerative Colitis by Acting on Gut Microbiome to Produce Butyric Acid

Taxifolin is a bioflavonoid which has been used to treat Inflammatory Bowel Disease. However, taxifolin on DSS-induced colitis and gut health is still unclear. Here, we studied the effect of taxifolin on DSS-induced intestinal mucositis in mice. We measured the degree of intestinal mucosal injury and inflammatory response in DSS treated mice with or without taxifolin administration and studied the changes of fecal metabolites and intestinal microflora using 16S rRNA. The mechanism was further explored by fecal microbiota transplantation. The results showed that the weight loss and diarrhea score of the mice treated with taxifolin decreased in DSS-induced mice and longer colon length was displayed after taxifolin supplementation. Meanwhile, the expression of GPR41 and GPR43 in the colon was significantly increased by taxifolin treatment. Moreover, the expression of TNF-α, IL-1β, and IL-6 in colon tissue was inhibited by taxifolin treatment. The fecal metabolism pattern changed significantly after DSS treatment, which was reversed by taxifolin treatment. Importantly, taxifolin significantly increased the levels of butyric acid and isobutyric acid in the feces of DSS-treated mice. In terms of gut flora, taxifolin reversed the changes of Akkermansia, and further decreased uncultured_bacterium_f_Muribaculaceae. Fecal transplantation from taxifolin-treated mice showed a lower diarrhea score, reduced inflammatory response in the colon, and reduced intestinal mucosal damage, which may be related to the increased level of butyric acid in fecal metabolites. In conclusion, this study provides evidence that taxifolin can ameliorate DSS-induced colitis by altering gut microbiota to increase the production of SCFAs.

Using Machine Learning to Identify Metabolomic Signatures of Pediatric Chronic Kidney Disease Etiology

BACKGROUND

Untargeted plasma metabolomic profiling combined with machine learning (ML) may lead to discovery of metabolic profiles that inform our understanding of pediatric CKD causes. We sought to identify metabolomic signatures in pediatric CKD based on diagnosis: FSGS, obstructive uropathy (OU), aplasia/dysplasia/hypoplasia (A/D/H), and reflux nephropathy (RN).

METHODS

Untargeted metabolomic quantification (GC-MS/LC-MS, Metabolon) was performed on plasma from 702 Chronic Kidney Disease in Children study participants (n: FSGS=63, OU=122, A/D/H=109, and RN=86). Lasso regression was used for feature selection, adjusting for clinical covariates. Four methods were then applied to stratify significance: logistic regression, support vector machine, random forest, and extreme gradient boosting. ML training was performed on 80% total cohort subsets and validated on 20% holdout subsets. Important features were selected based on being significant in at least two of the four modeling approaches. We additionally performed pathway enrichment analysis to identify metabolic subpathways associated with CKD cause.

RESULTS

ML models were evaluated on holdout subsets with receiver-operator and precision-recall area-under-the-curve, F1 score, and Matthews correlation coefficient. ML models outperformed no-skill prediction. Metabolomic profiles were identified based on cause. FSGS was associated with the sphingomyelin-ceramide axis. FSGS was also associated with individual plasmalogen metabolites and the subpathway. OU was associated with gut microbiome-derived histidine metabolites.

CONCLUSION

ML models identified metabolomic signatures based on CKD cause. Using ML techniques in conjunction with traditional biostatistics, we demonstrated that sphingomyelin-ceramide and plasmalogen dysmetabolism are associated with FSGS and that gut microbiome-derived histidine metabolites are associated with OU.

Xenobiotic receptors and the regulation of intestinal homeostasis: harnessing the chemical output of the intestinal microbiota

The commensal bacteria that reside in the gastrointestinal tract exist in a symbiotic relationship with the host, driving the development of the immune system and maintaining metabolic and tissue homeostasis in the local environment. The intestinal microbiota has the capacity to generate a wide array of chemical metabolites to which the cells of the intestinal mucosa are exposed. Host cells express xenobiotic receptors, such as the aryl hydrocarbon receptor (AhR) and the pregnane X receptor (PXR), that can sense and respond to chemicals that are generated by nonhost pathways. In this review, we outline the physiological and immunological processes within the intestinal environment that are regulated by microbial metabolites through the activation of the AhR and the PXR, with a focus on ligands generated by the stepwise catabolism of tryptophan.

Flavonoid-Amyloid Fibril Hybrid Hydrogels for Obesity Control via Construction of Gut Microbiota

Innovative precise clinical approaches to protect humans from the alarming global growth of epidemics of chronic diseases, such as metabolic syndrome (MetS), are urgently needed. Here, we introduce protein hydrogels...

The Mechanism Underlying the Influence of Indole-3-Propionic Acid: A Relevance to Metabolic Disorders

The increasing prevalence of metabolic syndrome has become a serious public health problem. Certain bacteria-derived metabolites play a key role in maintaining human health by regulating the host metabolism. Recent evidence shows that indole-3-propionic acid content can be used to predict the occurrence and development of metabolic diseases. Supplementing indole-3-propionic acid can effectively improve metabolic disorders and is considered a promising metabolite. Therefore, this article systematically reviews the latest research on indole-3-propionic acid and elaborates its source of metabolism and its association with metabolic diseases. Indole-3-propionic acid can improve blood glucose and increase insulin sensitivity, inhibit liver lipid synthesis and inflammatory factors, correct intestinal microbial disorders, maintain the intestinal barrier, and suppress the intestinal immune response. The study of the mechanism of the metabolic benefits of indole-3-propionic acid is expected to be a potential compound for treating metabolic syndrome.

Leveraging the Microbiome for Obesity: Moving From Form to Function

Treatment of obesity, an ongoing global epidemic, is challenging, as weight-loss efforts require a multidisciplinary approach addressing both behavioral and biologic needs that are not completely understood. Recent studies of the gut microbiome may provide better insight into the condition, and ultimately serve to advance more effective therapies. Research in this field has shifted from analyzing microbiome compositional differences to investigating functional changes that affect disease pathophysiology and outcome. Bacteria-derived metabolites are a way to bridge compositional changes to functional consequences. Through the production of metabolites, such as short chain fatty acids, tryptophan derivatives and bile acids, and interactions with peripheral and central signaling pathways, the gut microbiome may alter the body's metabolic and behavioral responses to food. Here, we summarize these mechanisms driven by gut-derived metabolites, through which the microbiome is thought to contribute to obesity, as well as review recent investigations of interventions related to these metabolites. Limitations of existing research, primarily due to paucity of causal studies in humans, are also discussed in this review.

Multi-Omic Approaches to Identify Genetic Factors in Metabolic Syndrome

Metabolic syndrome (MetS) is a highly heritable disease and a major public health burden worldwide. MetS diagnosis criteria are met by the simultaneous presence of any three of the following: high triglycerides, low HDL/high LDL cholesterol, insulin resistance, hypertension, and central obesity. These diseases act synergistically in people suffering from MetS and dramatically increase risk of morbidity and mortality due to stroke and cardiovascular disease, as well as certain cancers. Each of these component features is itself a complex disease, as is MetS. As a genetically complex disease, genetic risk factors for MetS are numerous, but not very powerful individually, often requiring specific environmental stressors for the disease to manifest. When taken together, all sequence variants that contribute to MetS disease risk explain only a fraction of the heritable variance, suggesting additional, novel loci have yet to be discovered. In this article, we will give a brief overview on the genetic concepts needed to interpret genome-wide association studies (GWAS) and quantitative trait locus (QTL) data, summarize the state of the field of MetS physiological genomics, and to introduce tools and resources that can be used by the physiologist to integrate genomics into their own research on MetS and any of its component features. There is a wealth of phenotypic and molecular data in animal models and humans that can be leveraged as outlined in this article. Integrating these multi-omic QTL data for complex diseases such as MetS provides a means to unravel the pathways and mechanisms leading to complex disease and promise for novel treatments. © 2022 American Physiological Society. Compr Physiol 12:1-40, 2022.

Enhanced Intestinal Barriers by Puerarin in Combination with Tryptophan

The intestinal barrier is essential for maintaining human intestinal health. The growing number of studies has shown that both puerarin and tryptophan and its metabolites have a beneficial effect on the intestinal barrier. This study aims at the combination of puerarin and tryptophan or its metabolites for improving the intestinal barrier. In our study, 40 female Sprague-Dawley rats were randomly divided into five groups (n = 8) for a 4-week experiment and dextran sodium sulfate was used to induce an intestinal barrier injury in rats. Our results showed that puerarin combined with tryptophan or its metabolites (indole-3-propionic acid, IPA) improved the intestinal barrier by enhancing the mucus layer barrier, which was mainly achieved by increasing the number of goblet cells and promoting the secretion of MUC2. Both TRPM5 and VAMP8 promoted MUC2 secretion in goblet cells through exocytosis, but their mechanisms of action are different. In our study, we found that puerarin and tryptophan showed different effects on TRPM5 and VAMP8, respectively. Puerarin enhances the expression of TRPM5, and tryptophan inhibits the expression of TRPM5; however, puerarin and tryptophan have no significant effect on the expression of VAMP8.

Association between gut microbiota and elevated serum urate in two independent cohorts

OBJECTIVES

Hyperuricemia is a precursor to gout and is often present in other metabolic diseases that are promoted by microbiome dysbiosis; however, no study has examined the association of gut microbiota with hyperuricemia and serum urate in humans.

METHODS

Study participants were derived from a community-based observational study, the Xiangya Osteoarthritis Study (discovery cohort). Hyperuricemia was defined as the presence of serum urate level >357 μmol/L for women and >416 μmol/L for men. Gut microbiota was analyzed using 16S rRNA sequencing from stool samples. We examined the relation of microbiota dysbiosis (i.e., richness, diversity, composition, and relative abundance of microbiota taxa) and predicted functional pathways to prevalent hyperuricemia and serum urate levels. We verified the associations in an independent observational study, the Step Study (validation cohort).

RESULTS

The discovery cohort consisted of 1,392 rural participants (mean age: 61.3 years; women: 57.4%; hyperuricemia: 17.2%). Participants with hyperuricemia had decreased richness and diversity, altered composition of microbiota, and lower relative abundances of genus Coprococcus compared with those with normouricemia. Predicted Kyoto Encyclopedia of Genes and Genomes metabolism pathways belonged to amino acid and nucleotide metabolisms were significantly altered in individuals with hyperuricemia compared with those with normouricemia. Gut microbiota richness, diversity and low relative abundances of genus Coprococcus were also associated with high levels of serum urate. These findings were replicated in the validation cohort with 480 participants.

CONCLUSIONS

Gut microbiota dysbiosis was associated with elevated serum urate levels. Our study raises the possibility that microbiota dysbiosis may modulate serum urate levels.

Electroacupuncture interventions alleviates myocardial ischemia reperfusion injury through regulating gut microbiota in rats

Electroacupuncture (EA) intervention has a remarkable cardioprotection against myocardial ischemia reperfusion injury (MIRI). Recently, it has been suggested that the gut microbiota plays an important role in regulating the progression and prognosis of MIRI. The purpose of this study was to illustrate the relationship between gut microbiota and cardioprotection of EA on MIRI. We conducted a MIRI model by ligating the left anterior descending coronary artery for 30 min followed by reperfusion in male Sprague Dawley rats, which then received 7 days of EA intervention. Echocardiography was employed to evaluate left ventricular function. Fecal samples were collected for microbial analysis by 16S rDNA high-throughput sequencing. Blood samples and myocardium were collected for inflammatory cytokine detection by enzyme linked immunosorbent assay (ELISA) and Western blot. Hematoxylin & eosin (HE) staining and immunofluorescence of ileum tissue were performed for intestinal damage evaluation. After 7 days of EA intervention, the left ventricular function was improved with significantly increased ejection fraction and fractional shortening. Furthermore, we found that EA intervention reversed the changed gut microbiota induced by MIRI, including Clostridiales, RF39, S24-7, Desulfovibrio, and Allobaculum, improved the impaired gut barrier, reduced the production and circulation of lipopolysaccharide (LPS), inhibited the level of interleukin 6 (IL-6) and interleukin 12 (IL-12) in periphery and decreased the expression of Toll like receptor 4 (TLR4) and IL-6 in myocardium. EA intervention could improve the impaired gut mucosal barrier and reduce the production and circulation of LPS after MIRI through regulating gut microbiota, thus inhibiting the circulation and myocardium inflammation and finally exerted the cardioprotective effect.